Thread Content
Application Analysis of Low-Water Moisture Quenching Technology for Coke Quenching Current Status of Coke Quenching Technology Coke quenching technology is divided into wet and dry methods. Dry quenching of coke offers environmental benefits and enables the recovery of thermal energy; it was expected to be widely adopted. However, due to high investment and operating costs, its widespread use is not feasible in the short term. As a result, adopting better low-water quenching technologies has become an option considered for the renovation of many existing plants as well as for the construction of new coking plants. At the same time, as low-water coking technology continues to be improved, it exhibits performance equal to or even better than that of dry methods in terms of environmental protection and other aspects. For decades, wet quenching of coke has been a backward process that involves spraying water through holes in pipes; **these holes often get clogged, and when the quenching time is too long the moisture content is high, while if the time is too short red coke is produced. As a result, the strength and moisture content of the coke after quenching are not stable. Overview of Spray Low-Water Coking Quenching Technology The spray low-water coking quenching technology is a proprietary technology of the American Spray Company. This technology achieves coke quenching by spraying water through nozzles installed above the original coke quenching vehicle throughout the entire quenching process. The principle behind it is that the water sprayed from the nozzles exerts a strong force with even distribution; this causes the large amount of steam generated upon contact with the high-temperature coke (with an upward velocity of up to 15 m/s) to be confined and circulate around the coke vehicle, thereby preventing the coke from coming into contact with the surrounding air and achieving quenching through suffocation. According to foreign tests, under conditions where air is isolated by **fog, an open flame can be extinguished within 3 seconds, with the remaining **being used only for cooling the coke and adjusting its moisture content. Therefore, the coking time can be reduced, and the moisture content of coke can be maintained at a set value over the long term ； This set value can be controlled as needed, with a minimum of 2.5%. The coke strength M25 increased by about 1%. Spraying low-water quenching causes the coke temperature to drop rapidly, shortening the reaction time for the formation of water gas and H2S, and reducing harmful components such as CO and H2S in the exhaust steam. Other advantages include: a significant reduction in the amount of steam discharged (by 30%–50%), with almost no coke dust entrained. This will help control dust and odors around the coking plant, resulting in a significant improvement in air quality. Due to the use of specialized nozzles with a large aperture (over 50 mm), it is possible to utilize wastewater or recycled water from coking plants; in other words, the nozzles have no requirements regarding water quality, and approximately 0.3–0.5 tons of wastewater can be used per ton of coke processed. Modifying the existing coke quenching system is quite straightforward; only a few steps are required (taking a 4.3m coke oven as an example): 1) While keeping the existing water supply pumps, valves, main water pipes, and branch pipes unchanged, two new water supply pipes need to be fabricated. This minimizes the modification time and amount required, and can be completed using production downtime. 2) Install nozzles on the two new branch pipes. Parameters such as nozzle height, tube spacing, and nozzle spacing need to be strictly controlled in accordance with the relevant design requirements ； 3) For the renovation, cast iron pipes can be used, as well as steel pipes, of the same grade as the original ones ； 4) The pressure at the nozzle inlet is greater than 1 bar ； If the water pump cannot maintain an inlet pressure of more than 1 bar, it can still be used, but its performance will be significantly reduced. Effects achieved after the renovation In May 2002, Hangzhou Iron and Steel Co.’s coking plant was the first in China to adopt this technology. Today, more than 30 coking plants have adopted it. The coking plant of Hebei Handan Iron and Steel Company uses both dry quenching of coke, as well as the low-water quenching technology, which was among the first to be introduced in China. In 2005, the last two coke quenching towers were upgraded to use the spray-based low-water quenching technology. Production practice has shown that using this technology results in significant cost savings, short renovation times, and excellent outcomes. The main advantages include: a coke moisture content of around 3% without the need for pre-drying. According to the relevant assessment results, for every 1% decrease in the moisture content of coke, the coke ratio used in iron production can be reduced by about 2%, and the cost per ton of iron can be lowered by approximately 6 yuan. Stabilizing and reducing coke moisture yields significant energy-saving and economic benefits. The quenching time can be reduced to about 70–90 seconds, which is only about half of the traditional coking quenching time. The nozzle is not clogged; unlike the original system, which often gets clogged or fails to seal the tube ends to discharge coke particles. Due to the absence of intense agitation of the coke caused by water entering the bottom of the coke oven, there is less mechanical damage to the coke ； There was also no issue of coke bouncing out of the coke car. Due to its **strong and uniform action, the amount of coke powder carried in the steam is significantly reduced, which not only cuts down waste but also controls dust pollution. The water vapor released when the engine is turned off is significantly reduced, which in turn leads to a decrease in the amount of water that needs to be added; this amount is reduced by about 50% ； The nozzle orifice is not prone to clogging ； **It can cover the coke on the furnace car completely, preventing it from coming into contact with air, and thus can cause the coke to go out due to lack of oxygen within a few seconds; as a result, there is no red coke ； The strength of the coke increases by about 1%, with an M25 value of 90%–91%. Conclusion Due to its simplicity and practicality, the low-moisture wet quenching method is increasingly adopted by steel companies. In particular, for coking plants that previously used the wet quenching process, implementing this method requires only minor modifications, with little impact on production time. Nearly 20 coking plants in China, including Benxi Steel, Tangsteel, and Handan Iron and Steel, have already adopted this technology.